Plasma may be used in various processes for physically and/or chemically altering a surface of a workpiece. For example, plasma may be used to deposit or spray a layer of material onto a workpiece, to etch or sputter away unwanted material from a workpiece, or to perform ashing or stripping processes on a workpiece. Typically, plasma is generated using a plasma generator, which may include a tube, a coil, and a processing gas source. The tube may be made of a dielectric material, such as quartz or aluminum/sapphire, and may be at least partially surrounded by the coil. An inner surface of the tube defines a plasma chamber that is in flow communication with the processing gas source to receive a processing gas. To diffuse the processing gas before injection into the plasma chamber, a gas flow distribution receptacle may be disposed over an inlet thereof.
During operation, the coil is energized to create an electric field across the plasma chamber. As the processing gas flows through the electric field, a portion of the processing gas transforms into a plasma, which may include species such as electrons, ions, and reactive radicals. The plasma species flow to the workpiece, and depending on the particular process in which the plasma is used, may deposit onto the workpiece to form a layer or may react with materials on the workpiece to form removable species.
Although the aforementioned system yields high quality plasma, the system may be improved. For example, high voltages (e.g. greater than 5 kV) may be supplied to the coil to maintain plasma production; however, if the high voltages are applied beyond a threshold period of time, or above a threshold voltage, ions may form that bombard or sputter on the surfaces of the tube. As a result, the tube and/or surrounding components may have a shortened lifespan and maintenance thereof may be undesirably frequent. To at least partially alleviate this effect, a Faraday shield may be disposed between the tube and the coil; however, such a configuration may add complexity and costs to the system. In another example, in some configurations, plasma may flow from a plasma region in the tube having a small diameter (e.g., about 76 mm) to a distribution region in the tube having a larger diameter (e.g., about 300 mm), hence decreasing the density of plasma from region to region. As a result, the rate at which the ionized gas dissociates into reactive radicals may also vary, which may lead to a longer process duration than desired.
Accordingly, it is desirable to have an improved plasma generator system that may cause minimal ion bombardment and/or sputtering of its system components. Additionally, it is desirable for the plasma generator system to include components, such as gas flow distribution receptacles and tubes, with improved useful lives compared to components of conventional plasma generator systems to thereby decrease maintenance costs of such systems. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.